In recent years, numerous studies have shown the negative health effects of high consumption of simple sugars and the positive health benefits of increasing the soluble dietary fiber in human diets. In response to these studies and the popularity of certain diets that emphasize the reduction of glycemic load, consumers demand lower glycemic index foods, which are less sugary and higher in soluble dietary fiber. To meet this demand, the food industry has given particular attention to a number of substitutes for the traditional sugary carbohydrates. These include non-nutritive sweeteners, sugar alcohols, isomaltooligosaccharides and fructooligosaccharides. Particular interest has been directed to the fructooligosaccharides (FOSs). These compounds impart mild sweetness, but also significantly, they are soluble dietary fibers with documented health benefits. FOSs are found naturally in, for example, banana, tomato, onion and numerous other plant sources. For commercial use, FOSs are produced enzymatically from sucrose using fructosyltransferase enzymes. FOSs are commercially available as a nutritional supplement and have Generally Recognized As Safe (GRAS) status. While publications exist on the use of FOS as a nutritional supplement, disclosed herein is a novel in situ process to convert endogenous or naturally occurring sucrose in a food product to a soluble dietary fiber (e.g., FOS) by contacting the food product with a fructosyltransferase.